Double emulsions of water-in-oil-in-water stabilized by alpha-form fat microcrystals. Part 1: Selection of emulsifiers and fat microcrystalline particles

Double emulsions are commonly stabilized by monomeric and/or polymeric emul sifiers. Pickering stabilization by solid particles such as colloidal micro crystalline cellulose has been mentioned only once as a possible technique to stabilize the external interface of the water-in-oil-in-water emulsion. No further work was carried out exploring this option. The present study sh ows that solid microcrystalline fat particles of alpha-form are capable of adsorbing at the water-oil interface and, together with other hydrophobic e mulsifiers, can stabilize water-in-oil (W/O) emulsions. The crystals must b e submicron in size in order to effectively adsorb and arrange at the inter face. Large crystals do not fit and were found to flocculate as free crysta ls in the continuous oil phase. The alpha-form crystals can be obtained by flash-cooling saturated triglycerides in vegetable oils in the presence of emulsifiers, such as polyglycerol polyricinoleate (PGPR), that stabilize th e dispersion and serve as alpha-tending crystal structure modifiers. It was assumed that PGPR also serves as a cross-linker or bridge between the crys talline fat particles and the water, and facilitates the anchoring of the f at particles in the oil phase in one direction while dangling itself in the water phase. The double emulsion droplets prepared with these W/O emulsion s are relatively large in size (6-18 mu m), but stable to coalescence. The marker (NaCl) does not seem to release with time, suggesting that the fat p articles form microcapsules on the water interface, totally sealing the wat er from releasing its addenda. The systems seem to have a significant poten tial for food emulsions.